WE ARE bombarded with health claims but how many are accurate or based on any real science? In a new series on BBC Two, Trust Me I'm A Doctor, I test them out. These are a few common myths.

When scientists followed 130,000 men and women, ranging from heavy coffee drinkers to those who hardly touched the stuff, they found that "regular coffee consumption was not associated with an increased mortality rate". In fact moderate coffee consumption appears to be mildly protective.

Based on this and other studies the most effective "dose" is two to five cups a day.

2) THERE'S NO SUCH THING AS A HEALTHY TAN

Too much sun causes skin damage, skin ageing and some forms of skin cancer but the most lethal form, melanoma, is actually more common in people who work indoors rather than outdoors.

Though it is not a good idea to use sunbeds or binge on sunshine there is evidence of benefits from regular sun exposure. The link is vitamin D, which we manufacture in our skin. Low levels of vitamin D are associated with increased risk of heart disease, stroke, schizophrenia, multiple sclerosis, asthma and a dozen cancers.

3) BEING OVERWEIGHT IS UNHEALTHY

The accepted wisdom is that if you have a body mass index (BMI) of between 25-30 then you are overweight and this is unhealthy. So a review in the Journal Of The American Medical Association caused a stir when scientists put forward evidence that mildly overweight people live longer than people considered a healthy weight.

One of the problems with defining obesity by using BMI (calculated by dividing your weight in kilograms by your height in metres squared) is it can be misleading, particularly if you have a lot of muscle or are tall. Also being fit and overweight is healthier than being unfit and slim.

4) A COUPLE OF GLASSES OF RED WINE A DAY ARE GOOD FOR YOU

The upside of drinking modest amounts of alcohol is that it may protect against heart disease. The downsides of drinking alcohol are the increased risk of liver disease and cancer. Dr Peter Scarborough, of the University of Oxford, says that the downside swiftly displaces the upside and that half a unit (about a quarter of a glass of wine) a day is the optimum amount from a health perspective. "If you're drinking more than that then you are not at the best level for reduced risk," he says.

5) EATING 'FIVE A DAY' CUTS YOUR RISK OF CANCER

A review in the British Journal Of Cancer looking into the links between eating fruit and vegetables and cancer risk concluded that: "No protective effects have been firmly established."

It is more likely that some fruit and vegetables protect against some cancers. The World Cancer Research Fund suggests that broccoli, cabbage and onions will "probably" protect against cancers of the mouth, oesophagus and stomach. Tomato and tomatobased products "may" reduce the incidence of prostate cancer. That said, eating fruit and veg will protect against heart disease and other chronic diseases and is certainly better than eating junk food.

6) WE ALL NEED TO DRINK TWO LITRES OF WATER A DAY

The mythical figure of two litres probably dates back to the Forties when researchers calculated this was how much water we used in 24 hours. However the researchers also said that we get much of the water we need each day from our food. Drinks such as coffee and tea also count, despite what many people believe. Drinking eight glasses of cold water a day could help you lose weight because you would use energy, about 70 calories, raising that water to body temperature. Apart from that, if you just drink when you're thirsty you'll be fine.

7) CRACKING YOUR KNUCKLES CAUSES ARTHRITIS

A delightful piece of research was done some years ago by Dr Donald Unger. For 50 years he cracked the fingers of his left hand but left the right totally free. And what did he find? No arthritis in either hand. So what makes that cracking noise? Its probably just the sound of gases in our joints filling a vacuum as we stretch them.

So a review in the Journal Of The American Medical Association caused a stir when scientists put forward evidence that mildly overweight people live longer than people considered a healthy weight

8) EATING EGGS WILL RAISE YOUR CHOLESTEROL

Many people believe eating eggs is bad for you because eggs contain cholesterol. But the fact is that most of the cholesterol in your blood is produced by your liver and is in response to eating too much saturated fat, not cholesterol. When scrambled, boiled, poached or in a healthy omelette, eggs are a superb source of protein, rich in vitamins and make a great start to the day.

9) LISTENING TO MOZART CAN MAKE YOU MORE INTELLIGENT

This myth is based on a 1993 study in which a team from the University of California exposed people to Mozart's music. They did seem to get better at solving simple puzzles but the effects were short-lived: only 15 minutes. And Mozart doesn't seem to be that special. In the short term any music you like can help you to be more alert, more focused and to concentrate. It won't make you more intelligent.

10) SMOOTHIES ARE A HEALTH DRINK

Smoothies have a reputation for being healthy because they are based on fruit but by the time you get rid of the fibre and the peel you have lost many of the potential health benefits. A survey reveals that out of 52 commercial smoothies 41 had more sugar than cola and all had more calories. They are also acidic and the bits cling to your teeth so dentists are not keen. An apple a day may keep the doctor away but not when it's peeled, blended, mashed and packaged.

Trust Me I'm A Doctor is on BBC Two, 8pm, tomorrow, followed at 9pm on BBC Four by Michael's other new series Pain, Pus And Poison.